Prefabricated concrete elements of various types are commonly used in building for the construction of various types of buildings, especially multi-story buildings, such as residential buildings, schools, hospitals, offices and hotels. In this type of technology, a frame is generally assembled on the construction site, consisting of prefabricated concrete elements, such as pillars, beams and floors, having a substantially linear geometry. Such prefabricated elements are produced in special production sites quicker than when they are produced at the final construction site. The assembly of the prefabricated elements generally includes the steps of positioning and then joining them by wet connections or by welding metal inserts, so as to obtain sufficient stiffness of the panel points between the elements, further requiring appropriate shoring.
Disadvantageously, the assembly of such traditional prefabricated elements is particularly long and impractical, typically including, for each building story, the steps of:                assembling and shoring the vertical elements (columns, pillars);        assembling and shoring the horizontal elements (beams);        assembling and shoring the floor elements;        implementing the connections using additional casting and armors;        waiting for the partial or complete curing of the additional casting;        disassembling and recovering the props, following an adequate curing of the concrete of the panel points or of the full sections of the structural elements.        
Thereafter, the assembly operations continue as a function of the desired number of building stories through a new cycle of vertical progress.
Disadvantageously, all of these operations require quite long times, especially if compared with the high production speed of the elements which are prefabricated in factories, made ad hoc, therefore they hold back a progress of the works which could be much faster.
The number of pieces to be mounted, the operations needed to ensure a condition of sufficient static and adjustment stability of the vertical and horizontal levels also require long times.
In addition, disadvantageously, a large, highly qualified staff is required for the assembly of such structures.
A further drawback associated with traditional prefabricated concrete elements is that the above assembly operations can be strongly influenced by the different climatic zones where the assembly is carried out, such as: zones with strong solar radiation and high temperatures, such as the Middle East, desert areas, etc.; or areas with high rainfall, particularly with strong rains, such as the areas of the Equatorial belt; or areas with very cold climates, where temperatures are often below 0° C., as in the zones of the North, Russia, Scandinavia, etc.
In order to operate properly in these climates, the assembly time on-site should be reduced as much as possible, such as trying to make the largest possible number of operations at production factories other than the building yard where the prefabricated elements are assembled.
U.S. Pat. No. 3,613,325 describes a system in which only two prefabricated components are provided: floor panels and structural units consisting of a horizontal beam placed between one or more upper columns and one or more lower columns. Disadvantageously, such structural units are laterally connected to one another through concrete castings made on site, for which the construction times are still long and shoring and formworks are needed, since the system is not self-supporting in all the building steps. The mode of vertically connecting the structural units also leaves room for improvement. In fact, in order to connect a lower structural unit to an upper structural unit, an expansion mortar must be cast in the sleeves which house the connecting bars. Shoring is also required during this operation since the connection between connecting bars and sleeves is not stable without applying the mortar.
In summary, for the construction of buildings, particularly multi-story buildings, with construction techniques using prefabricated concrete elements, an important step which requires long times and particular attention to details, resulting in a high probability of making mistakes, and which is strongly influenced by climatic factors, is the assembly of such prefabricated elements at the construction site.
The need to implement a building system for multi-story buildings allowing said drawbacks to be overcome is therefore felt.